High selectivity chemically cross-linked rubbery membranes and their use for separations

a chemically crosslinked rubber and high selectivity technology, applied in the field of high selectivity chemically crosslinked rubbery membranes and their use for separation, can solve the problems of olefin recovery, liquefied, lpg) recovery, and the performance of membranes prepared from glassy polymers is not outstanding for organic vapor separation, and achieves the effects of improving the permeance and selectivity, increasing the plasticization of condensable olefins, and increasing the permeation ra

Inactive Publication Date: 2018-05-17
UOP LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012]Different from glassy polymeric membranes that are highly selective to gases with smaller kinetic diameters over larger diameter gases, the new chemically cross-linked rubbery polymeric TFC membrane comprising a thin selective layer of a chemically cross-linked rubbery polymer on top of a porous support membrane formed from a glassy polymer disclosed in the present invention is highly selective to olefins and heavier hydrocarbons over methane and inert gases such as N2 and H2. In addition, opposite from glassy polymeric membranes, the new chemically cross-linked rubbery polymeric TFC membrane described in the current invention has improved permeance and selectivity with the increase of operating time due to the increase of plasticization of condensable olefins on the membrane or with the decrease of operating temperature.

Problems solved by technology

These membranes prepared from glassy polymers, however, do not have outstanding performance for organic vapor separations such as for olefin recovery, liquefied petroleum gas (LPG) recovery, fuel gas conditioning, natural gas dew point control, nitrogen removal from natural gas, etc.
There are, however, several other obstacles to use a particular polymer to achieve a particular separation under any sort of large scale or commercial conditions.
One such obstacle is permeation rate or flux.
Plasticization occurs when one or more of the components of the mixture act as a solvent in the polymer often causing it to swell and lose its membrane properties.
It has been found that glassy polymers such as cellulose acetate and polyimides which have particularly good separation factors for separation of mixtures comprising carbon dioxide and methane are prone to plasticization over time thus resulting in decreasing performance of these membranes.
Natural gas often contains substantial amounts of heavy hydrocarbons and water, either as an entrained liquid, or in vapor form, which may lead to condensation within membrane modules.
The presence of more than modest levels of liquid BTEX heavy hydrocarbons is potentially damaging to traditional glassy polymeric membrane.
Therefore, precautions must be taken to remove the entrained liquid water and heavy hydrocarbons upstream of the glassy polymeric membrane separation steps using expensive membrane pretreatment system.
Another issue of glassy polymeric polymer membranes that still needs to be addressed for their use in gas separations in the presence of high concentration of condensable gas or vapor such as CO2 and propylene is the plasticization of the glassy polymer by these condensable gases or vapors that leads to swelling of the membrane as well as a significant increase in the permeance of all components in the feed and a decrease in the selectivity of the membranes.
Disposing of the vent stream in a flare or partial recovery of the valuable olefin or other monomers via a condensing process results in the loss of valuable monomers and undesired emissions of the highly reactive volatile monomers into the air.

Method used

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  • High selectivity chemically cross-linked rubbery membranes and their use for separations
  • High selectivity chemically cross-linked rubbery membranes and their use for separations
  • High selectivity chemically cross-linked rubbery membranes and their use for separations

Examples

Experimental program
Comparison scheme
Effect test

example 1

Preparation of 5DMS-TDI / PES-a TFC Membrane

[0036]A porous, asymmetric PES gas separation support membrane was prepared via the phase-inversion process. A PES-a membrane casting dope comprising PES 18-25 wt %, NMP 60-65 wt %, 1,3-dioxolane 10-15 wt %, glycerol 1-10 wt % and n-decane 0.5-2 wt % was cast on a nylon fabric then gelled by immersion in a 1° C. water bath for about 10 minutes, and then annealed in a hot water bath at 85° C. for about 5 minutes. The wet membrane was dried at 70° C. A 5 wt % DMS-TDI pre-cross-linked rubbery polymer solution was prepared by dissolving 6.0 g of an aminopropyl-terminated polydimethylsiloxane (Gelest catalog number: DMS-A21) and 0.25 g of 2,4-toluene diisocyanate (TDI) in 118.8 g of hexane at room temperature for about 10 min. The dried PES-a porous support membrane was coated with the 5 wt % DMS-TDI pre-cross-linked rubbery polymer solution, dried at room temperature for about 5 min, and then heated at 85° C. for 2 h to form a thin, nonporous, d...

example 2

Preparation of 6.5DMS-TDI / PES-a TFC Membrane

[0037]A 6.5DMS-TDI / PES-a TFC membrane was prepared using the procedure described in Example 1 except that the PES-a support membrane was coated with a 6.5 wt % DMS-TDI pre-cross-linked rubbery polymer solution comprising 6.0 g of DMS-A21 and 0.25 g of 2,4-toluene diisocyanate (TDI) in 89.9 g of hexane at room temperature for about 10 min. The coated membrane was dried at room temperature for about 5 min, and then heated at 85° C. for 2 h to form a thin, nonporous, dense, chemically cross-linked DMS-TDI selective layer on the surface of the PES-a support membrane (abbreviated as 6.5DMS-TDI / PES-a). The 6.5DMS-TDI / PES-a TFC membrane was tested with a fuel gas mixture of 70% C1, 15% C2, 10% C3 and 5% CO2 at 3549 kPa (500 psig) and 25° C. The membrane was also tested with N2, H2, CH4, propylene, and propane single gases at 791 kPa (100 psig) and 25° C. The membrane permeances (P / L) and selectivities (α) are shown in Tables 1 and 2.

example 3

Preparation of 5DMS-TDI / 5DMS-TDI / PES-a Dual-Coated TFC Membrane

[0038]A 5DMS-TDI / 5DMS-TDI / PES-a dual-coated TFC membrane was prepared using the procedure described in Example 1 except that the PES-a support membrane was first coated with a 5 wt % DMS-TDI pre-cross-linked rubbery polymer solution comprising 6.0 g of DMS-A21 and 0.25 g of 2,4-toluene diisocyanate (TDI) in 118.8 g of hexane at room temperature for about 10 min. The coated membrane was dried at room temperature for about 5 min, and then heated at 85° C. for 2 h to form the first layer of thin, nonporous, dense, chemically cross-linked DMS-TDI on the surface of the PES-a support membrane. The DMS-TDI-coated PES-a TFC membrane was then coated with a 5 wt % DMS-TDI pre-cross-linked rubbery polymer solution again, dried at room temperature for about 5 min, and then heated at 85° C. for 2 h to form the second layer of thin, nonporous, dense, chemically cross-linked DMS-TDI on the surface of the DMS-TDI-coated PES-a TFC membra...

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Abstract

A novel chemically cross-linked rubbery polymeric thin film composite (TFC) membrane comprising a selective layer of a chemically cross-linked rubbery polymer supported by a porous support membrane formed from a glassy polymer has been developed. The chemically cross-linked rubbery polymeric thin film composite (TFC) membrane comprising a selective layer of a chemically cross-linked rubbery polymer supported by a porous support membrane formed from a glassy polymer may be used to separate at least one component from another.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority from Provisional Application No. 62 / 423,636 filed Nov. 17, 2016, the contents of which cited application are hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002]Over 170 Honeywell UOP Separex™ membrane systems have been installed in the world for gas separation applications such as for the removal of acid gases from natural gas, in enhanced oil recovery, and hydrogen purification. Two new Separex™ membranes (Flux+ and Select) have been commercialized recently by Honeywell UOP, Des Plaines, Ill. for carbon dioxide (CO2) removal from natural gas. These Separex™ spiral wound membrane systems currently hold the membrane market leadership for natural gas upgrading. These membranes prepared from glassy polymers, however, do not have outstanding performance for organic vapor separations such as for olefin recovery, liquefied petroleum gas (LPG) recovery, fuel gas conditioning, natural...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01D71/76B01D67/00B01D71/68B01D71/64B01D71/18
CPCB01D71/76B01D67/0006B01D71/18B01D71/64B01D71/68B01D69/10B01D69/125B01D71/16B01D71/24B01D71/70B01D2323/30B01D53/228B01D2256/24B01D2257/102B01D2257/108B01D2257/504B01D2257/7022B01D2257/7025C10L2290/548Y02C20/20Y02C20/40
Inventor LIU, CHUNQINGKARNS, NICOLE K.JAN, DENG-YANG
Owner UOP LLC
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